A phase shifter is a device for electrical beam tilting, which generates a phase difference of an input signal supplied to respective antenna radiating elements arranged in a row, thereby enabling electrical beam tilting. Specifically, a phase shifter may be implemented by generating a phase difference between the input signal and the output signal by appropriately delaying the supplied input signal and changing the physical length of the entire transmission line.
FIG. 1 is a view showing a conventional phase shifter, in which a variable substrate on which a second transmission line is formed is coupled to a top surface of a fixed substrate having a first transmission line formed on one surface thereof, and the variable substrate is rotated by a predetermined angle, thereby changing the physical length of the entire transmission line formed by connecting the two transmission lines to enable electrical beam tilting. However, since the overall structure of the phase shifter is a single layer, it is impossible to implement a multi-port shifter.
In addition, a sector antenna, which is commonly used according to recent developments of mobile communication technology, adopts a variable tilt method in order to obtain a high gain. To this end, a phase shifter is required to have multiple ports. If the phase shifter is implemented with multiple ports, the total volume of the phase shifter becomes larger than when the phase shifter is implemented with a single port, and thus installation thereof may be spatially restricted. Accordingly, the volume needs to be reduced.
Therefore, the present invention proposes a new multi-port phase shifter with a minimized volume that can implement multiple ports and thus be applied to a sector antenna for obtaining a high gain.